Proteus anguinus is a neotenic cave amphibian endemic to the Dinaric Karst and represents a symbol of Slovenian natural heritage. It is classified as ‘Vulnerable’ by the International Union for Conservation of Nature (IUCN) and is one of the EU priority species in need of strict protection. Due to inaccessibility of its natural underground habitat, scientific studies have been primarily conducted on Proteus in captivity where amphibians may be particularly susceptible to opportunistic microbial infections. In this case report we presented the results of an analysis of an individual that had been kept in captivity for 6 yr and then developed clinical symptoms, including ulcers, suggesting opportunistic microbial infection. Pigmented fungal hyphae and yeast-like cells were present in the dermis and in almost all other sampled tissues. Sampling of the ulcer allowed the isolation of a diverse array of bacterial and fungal species. We identified the water-borne, polymorphic black yeast Exophiala salmonis, an opportunistic pathogen of fish, as the cause of the primary infection. This is the first report on a fungal infection of Proteus and on cave salamanders in general.
COBISS.SI-ID: 4735311
In the last ten years, emerging pathogens have become one of the main causes of the global decline in amphibian populations, in particular skin infections by two fungal species, Batrachochytrium dendrobatidis ( Bd) and B. salamandrivorans (Bsal), as well as viral disease caused by the genus Ranavirus. Bd had never before been recorded in Slovenia, but it was known from all neighbouring countries. Bsal caused severe localized mortalities in natural populations of salamanders in The Netherlands, Belgium, Germany and Spain, but was also not recorded in Slovenia. Ranaviruses were reported across Western and Central Europe. We focused on the endemic olm (Proteus anguinus) and other Slovenian amphibians. Up to 2019 we collected swab samples from 173 live amphibians of 22 species from 53 natural sites across Slovenia and 41 samples of captive amphibians comprising 4 exotic and 6 native species. The sampling set comprised 70 olm individuals from five wild populations in Slovenia and 18 captive specimens. None of the 173 samples analyzed tested positive for ranavirus (MCP gene). Similarly, all samples were negative for Bsal, while a single individual of edible frog (Pelophylax kl. esculentus) sampled close to the northeastern border with Hungary tested positive for Bd by qPCR. Our study complements the data on the current range of Bd, Bsal and ranavirus in Europe as obtained by means of standardized screening protocols and provides the first record of Bd in Slovenia.
COBISS.SI-ID: 51755779
The European cave salamander Proteus anguinus is a charismatic amphibian endemic to the concealed and inaccessible subterranean waters of the Dinaric Karst. Despite its exceptional conservation importance not much is known about its ecology and interactions with the groundwater microbiome. The cutaneous microbiota of amphibians is an important driver of metabolic capabilities and immunity, and thus a key factor in their wellbeing and survival. We used high-throughput 16S rRNA gene sequencing based on seven variable regions to examine the bacteriome of the skin of five distinct evolutionary lineages of P. anguinus and in their groundwater environment. The skin bacteriomes turned out to be strongly filtered subsamples of the environmental microbial community. The resident microbiota of the analyzed individuals was dominated by five bacterial taxa. Despite an indicated functional redundancy, the cutaneous bacteriome of P. anguinus presumably provides protection against invading microbes by occupying the niche, and thus could serve as an indicator of health status. Besides conservation implications for P. anguinus, these results provide a baseline for future studies on other endangered neotenic salamanders.
COBISS.SI-ID: 4970319
Emerging infections add to existing threats to the survival of amphibians worldwide. The olm (Proteus anguinus) is a vulnerable, troglobiont urodele species with a small European range and restricted to underground karstic systems. Population declines to emerging threats like the chytrid fungus Batrachochytrium salamandrivorans, are likely to go unnoticed due to inaccessibility of the species’ habitat. We here studied the interaction between olms and B. salamandrivorans. Experimental inoculation of olms resulted in low-level, asymptomatic but persistent infections, with limbs as predilection sites. The lack of exponential fungal growth in the olms’ epidermis correlated with limited fungal proliferation and dampened virulence gene expression after exposure to olm skin compounds. The olm is one of few western Palearctic urodeles that is tolerant to B. salamandrivorans infection and may act as a subterranean disease reservoir, yet costs of subclinical infection may compromise olm fitness on the long term.
COBISS.SI-ID: 31433987
Although Proteus encounters various microorganisms and parasites in its natural environment, the records on them are scarce. The only comprehensive work on the topic dated, before the beginning of the project, to over half a century ago. From specimen in captivity it was known, although not published, that oomycoete water molds from the genus Saprolegnia sp., black yeasts and amoebae and bacterium Aeromonas hydrophila can cause occasionally infections.
COBISS.SI-ID: 4396879